where \(\theta \)  is varied in the range of \([0,180)\)  at an equal interval of \(20^\circ \) . The radial frequency is varied between \([0.7,1.5)\)  at an interval of \(0.2\) . Lee at el.[1]} have suggest to choose \(K\)  in the range of [2,2.5]. In this paper, \(K=2.2\)  is selected to accomplish better distinguishability between background and vessels. All these parameters are selected by performing few experiments on retinal images and Gabor wavelet filters. Fig. REF  shows few Gabor wavelet filters from the bank of filters for different radial frequency at orientation of 50o. The Gabor wavelet filter at \(\omega _0=0.7\)  is efficient to detect thick blood vessel. However, \(\omega _0=1.3\)  is suitable to detect thin blood vessels. The Gabor wavelet response of the preprocessed image is shown in Fig. REF .
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